Possibility to add builtin Pulsar Functions with a shared jar copied inside the function folder

Is your feature request related to a problem? Please describe. In order to create a pulsar function you have to build a fat jar (or nar) and the submit the jar when you create the function. The jar is copied by default inside pulsar/tmp/function_name. Currently it is not possible to load a shared jar containing one or more functions to be used without loading the jar (something similar to what is happening loading the a nar containing pulsar IO Sources/Sinks inside che connectors folder).

This could have the following benefits:

• Function can be distributed with the installation and users can create functions from builtin jars / nars without having the jar / nar file
• In case of multiple functions (with different functions names) using the same jar, the latter is not duplicated every time a new function is created

Describe the solution you’d like The possibility to create a new function loading the relative jar (if the function is not one of the builtin ones) or instantiate a new function using the builtin ones the are copied inside the function folder (like the connectors)

[nicolo-paganin]

@sijie I created a PR for this, could you please look at it? Thanks

[sijie]

@itaross I have included this task into the Pulsar release 2.6.0. If you have any features that would like to see in 2.6.0, please comment in #5819. We will prioritize those features.